The piezoelectric effect was discovered in 1880 when two scientists realized that pressure can generate electrical charges in a number of crystals, such as quartz, Rochelle salt and tourmaline. Pressure applied to the crystals generates electrical charges on the surface of piezoelectric materials. This is a direct piezoelectric effect, which is also called generator or sensor effect. It converts mechanical energy into electrical energy.
Because the early crystals did not develop a significant charge, there was little use of piezoelectric materials until a breakthrough was made in the discovery that polycrystalline ferroelectric ceramics such as barium titanate (BaTiO3) and lead zirconium titanate (PZT) induce piezoelectric characteristics on a useful scale. Special dopings of the PZT ceramics with e.g. Ni, Bi, La, Nd, Nb ions make it possible to specifically optimize piezoelectric and dielectric parameters. These polycrystalline ferroelectric ceramics led to numerous present day components that utilize the piezoelectric effect, such as lighters, loudspeakers and signal transducers.
The theory of how piezoelectric ceramics work teaches that mechanical stresses arising as the result of an external force that act on the piezoelectric body induce displacements of electrical dipoles within the piezoelectric ceramics. This generates an electric field, which produces a corresponding electric voltage. This direct piezoelectric effect is also called the sensor or generator effect, which can be used to ignite an explosive.
In the long history of the technology of warfare, a key turning point was the invention of gunpowder and various explosions. This was a quantum leap forward past the club; the sword, knife, and spear; and the bow and arrow. Now military planners could blow things up and harness explosive forces to propel projectiles toward the enemy.
When it comes to military explosives, one of the very important factors is the technological means used to detonate the explosive material. One of the primary detonation materials developed years ago in construction and mining industries was to have very long electrically conductive wires that would connect to the explosive and the other end would be connected to a charge plunger device that was safely far away. This charge plunger method is still in use today because it gives you specific timing control as to when you want the explosion to occur.
Other methods have been developed to have specific control of the timing of the explosion, which usually involves various types of wireless signals sent to a device that will then trigger the explosion. Many times in military situations these types of wireless detonators can be dangerous or unreliable because the enemy can either block the signal or send a signal of its own to cause an unwanted explosion.